Abstract
In 1962, Lwoff and his co-workers proposed a system of classification in which elongated plant viruses were classified as the group of the rod-shaped viruses. These viruses are non-enveloped, contain RNA, and have a helical symmetry. Some viruses are not easily classified in the system of Lwoff. An example is the case of alfalfa mosaic virus (AMV), a multicomponent virus. Some of its components appear to be elongated and their organization is unique; however, certainly nearer to cubic, than to helical symmetry. This chapter discusses the available information concerning the general structure and particular characteristics of the rod-shaped viruses and AMV. The tobacco mosaic virus (TMV) is a rod-shaped virus 3000 Å in length and 180 Å in width. The nucleic acid is RNA with a molecular weight of 2 X 106 daltons. TMV is constituted by 2200 morphological subunits, each with a molecular weight of approximately 17,000. In solution, TMV RNA is a random coil, of which 70% is in double-stranded form and 30% in single-stranded one. The disaggregation of TMV into its constituents may be easily obtained by various methods; however, it is difficult to simultaneously extract both viral nucleic acid and protein in undenatured form. The preparation of TMV protein is obtained by means of acetic acid and RNA by the bentonite–phenol method.
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